scholarly journals Spectroscopic evidence for a large spot on the dimming Betelgeuse

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sofya Alexeeva ◽  
Gang Zhao ◽  
Dong-Yang Gao ◽  
Junju Du ◽  
Aigen Li ◽  
...  
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Supernova Explosion ◽  
Spectroscopic Studies ◽  
Dark Spot ◽  
High Signal ◽  
Signal To Noise ◽  
Deep Minimum ◽  
Near Infrared Spectra

AbstractDuring October 2019 and March 2020, the luminous red supergiant Betelgeuse demonstrated an unusually deep minimum of its brightness. It became fainter by more than one magnitude and this is the most significant dimming observed in the recent decades. While the reason for the dimming is debated, pre-phase of supernova explosion, obscuring dust, or changes in the photosphere of the star were suggested scenarios. Here, we present spectroscopic studies of Betelgeuse using high-resolution and high signal-to-noise ratio near-infrared spectra obtained at Weihai Observatory on four epochs in 2020 covering the phases of during and after dimming. We show that the dimming episode is caused by the dropping of its effective temperature by at least 170 K on 2020 January 31, that can be attributed to the emergence of a large dark spot on the surface of the star.

scholarly journals 53 Piscium, an SPB Star with Activity

2002 ◽  
Vol 185 ◽  
pp. 236-237
Author(s):  
J.-M. Le Contel ◽  
P. Mathias ◽  
E. Chapellier ◽  
J.-C. Valtier
Keyword(s):  
High Resolution ◽  
False Alarm ◽  
High Frequency ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Correlation Technique ◽  
Signal To Noise ◽  
Spectroscopic Observations ◽  
Auto Correlation ◽  
Frequency Variations

The star 53 Psc (HD 3379, B2.5IV) has been observed as variable by several authors (Sareyan et al., 1979) with frequencies around 10 c d–1 and has been classified as a β Cephei star. Conversely, other authors (e.g. Percy, 1971) found it to be constant.New high resolution, high signal-to-noise ratio, Spectroscopic observations have been performed at the Observatoire de Haute-Provence in 1996 over 11 nights. The spectral domain covers around 200 Å and is centered on Hδ. Radial velocities were deduced from an auto-correlation technique with a scatter around 0.4kms−1.No high frequency variations are observed. Three frequencies have been detected with a false alarm detection above the 1 % level. A fourth one may be present but its amplitude is below this 1 % level. Results are displayed in Table 1.

scholarly journals The CARMENES search for exoplanets around M dwarfs

2020 ◽  
Vol 642 ◽  
pp. A227 ◽  
Author(s):  
C. Abia ◽  
H. M. Tabernero ◽  
S. A. Korotin ◽  
D. Montes ◽  
E. Marfil ◽  
...  
Keyword(s):  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Heavy Elements ◽  
High Signal ◽  
M Dwarfs ◽  
Chemical Enrichment ◽  
Near Infrared Spectra ◽  
Theoretical Predictions ◽  
History Of ◽  
First Time

Due to their ubiquity and very long main-sequence lifetimes, abundance determinations in M dwarfs provide a powerful and alternative tool to GK dwarfs to study the formation and chemical enrichment history of our Galaxy. In this study, abundances of the neutron-capture elements Rb, Sr, and Zr are derived, for the first time, in a sample of nearby M dwarfs. We focus on stars in the metallicity range − 0.5 ≲ [Fe/H] ≲ +0.3, an interval poorly explored for Rb abundances in previous analyses. To do this we use high-resolution, high-signal-to-noise-ratio, optical and near-infrared spectra of 57 M dwarfs observed with CARMENES. The resulting [Sr/Fe] and [Zr/Fe] ratios for most M dwarfs are almost constant at about the solar value, and are identical to those found in GK dwarfs of the same metallicity. However, for Rb we find systematic underabundances ([Rb/Fe] < 0.0) by a factor two on average. Furthermore, a tendency is found for Rb – but not for other heavy elements (Sr, Zr) – to increase with increasing metallicity such that [Rb/Fe] ≳ 0.0 is attained at metallicities higher than solar. These are surprising results, never seen for any other heavy element, and are difficult to understand within the formulation of the s- and r-processes, both contributing sources to the Galactic Rb abundance. We discuss the reliability of these findings for Rb in terms of non-LTE (local thermodynamic equilibrium) effects, stellar activity, or an anomalous Rb abundance in the Solar System, but no explanation is found. We then interpret the full observed [Rb/Fe] versus [Fe/H] trend within the framework of theoretical predictions from state-of-the-art chemical evolution models for heavy elements, but a simple interpretation is not found either. In particular, the possible secondary behaviour of the [Rb/Fe] ratio at super-solar metallicities would require a much larger production of Rb than currently predicted in AGB stars through the s-process without overproducing Sr and Zr.

scholarly journals The 12C/13C Ratio in Unevolved Cool Stars

1988 ◽  
Vol 132 ◽  
pp. 589-592
Author(s):  
Y. Chmielewski ◽  
D. L. Lambert
Keyword(s):  
High Resolution ◽  
Preliminary Analysis ◽  
Isotope Ratio ◽  
Signal To Noise Ratio ◽  
Carbon Isotope Ratio ◽  
High Signal ◽  
Reasonable Accuracy ◽  
Signal To Noise ◽  
Dwarf Stars ◽  
Cool Stars

We show that the carbon isotope ratio 12C/13C in the atmosphere of dwarf stars can be determined with reasonable accuracy from high resolution, high signal-to-noise ratio observations of the CH G-band in their spectra. Lines suitable for this purpose are selected from consideration of the solar case, for which 12C/13C = 89 is derived. A preliminary analysis of these features in the spectra of μ Her, δ Eri and τ Cet yields 12C/13C values of 84, 80 and 150 respectively.

scholarly journals Near-infrared turn-on fluorescent probe for discriminative detection of Cys and application in in vivo imaging

RSC Advances ◽  
2019 ◽  
Vol 9 (71) ◽  
pp. 41431-41437 ◽  
Author(s):  
Shaolong Qi ◽  
Lubao Zhu ◽  
Xinyu Wang ◽  
Jianshi Du ◽  
Qingbiao Yang ◽  
...  
Keyword(s):  
Fluorescent Probes ◽  
Biological Samples ◽  
In Vivo Imaging ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Biological Detection ◽  
Signal To Noise ◽  
Turn On

Near-infrared (NIR) fluorescent probes are widely employed in biological detection because of their lower damage to biological samples, low background interference, and high signal-to-noise ratio.

scholarly journals High Signal-To-Noise Ratio - the Spectroscopic Key to Algol Systems

1989 ◽  
Vol 107 ◽  
pp. 245-255
Author(s):  
Jocelyn Tomkin
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Large Fraction ◽  
High Signal ◽  
Signal To Noise ◽  
Algol System ◽  
Low Mass ◽  
Noise Ratio ◽  
Cno Abundances

AbstractThe usefulness of high signal-to-noise-ratio spectra for both radial-velocity and abundance studies of Algol systems is emphasised. It is shown that division by a hot star is a worthwhile step in pursuit of this objective. A preliminary analysis of high signal-to-noise-ratio, red and near-infrared, Reticon observations of R CMa shows that its primary has solar CNO abundances within the 0.3 dex observational error. The low-mass (0.17 m⊙) secondary of this Algol system must have lost a large fraction of its original mass. Some of this material would have been extensively processed during the secondary’s main-sequence lifetime and would therefore have had a highly non-solar CNO-abundance distribution. The lack of serious contamination of the primary’s abundances is consistent with most, but not all, plausible mass-transfer scenarios.

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